This invention relates in general to programmable logic controllers and, more particularly, to a method for configuring a smart module coupled to a programmable logic controller system.
Programmable logic controllers (PLC's) are a relatively recent development in process control technology. As a part of process control, a programmable logic controller is used to monitor input signals from a variety of input modules (input sensors) which report events and conditions occurring in a controlled process. For example, a PLC can monitor such input conditions as temperature, pressure, volumetric flow and the like. A control program is stored in a memory within the PLC to instruct the PLC what actions to take upon encountering particular input signals or conditions. In response to these input signals provided by input modules, the PLC derives and generates output signals which are transmitted to various output modules (output devices) to control the process. For example, the PLC issues output signals to open or close a relay, raise, or lower temperature, adjust pressure, or control the speed of a conveyer, as well as many other possible control functions.
Programmable logic controllers generally include a central processing unit which is coupled to a main bus into which a plurality of input modules and output modules are coupled. Input expansion boxes and output expansion boxes are usually connected to this main bus to facilitate the coupling of several input and output modules to the main bus of the controller.
Modern input and output modules are often rather complex in that they may contain a microprocessor and require substantial setup data from the user. A hand held programmer is generally used to configure such modules and to provide information about the modules to the programmable logic controller. This is a time consuming process in which the user is prompted with a series of questions by the hand held programmer and is required to provide answers which constitute configuration setup information. That is, the user interface which prompts the user with module setup questions is actually located in the hand held programmer software or the control program software for the PLC. Unfortunately, for this reason, in such PLC systems, the software which controls the PLC or the software which controls the hand held programmer must generally be rewritten to accommodate each new input module or output module which is developed.